Why do fruits get sweeter with time?
In: Biology
Plants can’t move and this makes it difficult for plants to get their seeds (their offspring) situated in a good location to sprout and grow far enough away from the mother-plant such that mother and offspring won’t compete for the same resources.
Some plants have solved this problem by evolving to make fruit in order to entice animals such as birds, bats, and monkeys to carry away their seeds and deposit those seeds far away from the mother-plant.
Think of edible fruit as a payment or bribe that the plant pays to the animal to perform the service of carrying the seeds far away.
While a fruit is still growing (i.e., unripe), the seed is not fully matured yet and so not ready to be planted. If an animal eats the fruit too soon, that defeats the purpose.
Accordingly, plants make their unripe fruit very unappetizing. Unripe fruits are hard, sour, bitter, astringent, and green like leaves to prevent animals from eating them too soon.
Then, once the seed is mature enough to be carried away, the fruit ripens and becomes delicious: sweet, soft, fragrant and brightly colored, in order to entice animals to come take the seeds away and drop them somewhere else.
In case you wanted to know “how”. Many unripe fruits are full of starch, which are long chains of sugar molecules linked together. Starches are not directly digestible by animals, don’t taste sweet, and are generally bland and gross. As the fruit ripens those starches are digested and broken down into their constituent sugar molecules, which obviously do taste sweet and delicious. As u/CalibanDrive notes, this digestion is specifically timed so that the fruit becomes delicious in concert with the fruit seeds reaching maturity.
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